Currently ACPI-driven alarms are not cleared when they wake the
system. As consequence, expired alarms must be manually cleared to
program a new alarm. Fix this by correctly handling ACPI-driven
alarms.
More specifically, the ACPI specification [1] provides for two
alternative implementations of the RTC. Depending on the
implementation, the driver either clear the alarm from the resume
callback or from ACPI interrupt handler:
- The platform has the RTC wakeup status fixed in hardware
(ACPI_FADT_FIXED_RTC is 0). In this case the driver can determine
if the RTC was the reason of the wakeup from the resume callback
by reading the RTC status register.
- The platform has no fixed hardware feature event bits. In this
case a GPE is used to wake the system and the driver clears the
alarm from its handler.